Plastics are materials that are indispensable in modern society. In general, plastic materials are susceptible to heat and are ignited or catch fire at a relatively low temperature. For fire-safety reasons, plastics used in electric or electronic devices, vehicle components and household articles should be resistant to the spread of fire. Thus, flame retardants are added to plastics to decrease their flammability. Some main flame retardants are bromine flame retardants, phosphorus flame retardants and inorganic flame retardants.
In particular, bromine flame retardants are categorized into monomer types and oligomer or polymer types. Recently, high-molecular weight oligomer- or polymer-type flame retardants are considered to be more environmentally friendly and safer for the human health, and are reported to outperform monomer-type flame retardants in various characteristics (for example, non-blooming properties and mechanical characteristics) (see, for example, “NAN-NEN-ZAI NO SAITEKI SHOHOU TO NENSHOU SHIKEN (optimum formulations of flame retardants and flame tests)”, TECHNICAL INFORMATION INSTITUTE CO., LTD., 2011, pp. 79-80, and WO 2008/134294).
For example, some main oligomer- or polymer-type flame retardants are brominated polystyrenes, brominated polyphenylene ethers, brominated benzyl acrylate polymers, brominated polycarbonate oligomers and brominated epoxies. These oligomer- or polymer-type bromine flame retardants are not applicable to all kinds of plastics and have inherent problems (see, for example, Japanese Patent Kohyo Publication No. 2001-517256).
While oligomer- or polymer-type flame retardants are used in marketplaces as described above, they are still incapable of satisfying all the performances required. Thus, those skilled in the art constantly demand new types of flame retardants.